"As the ambient temperature at a particular airport increases, in this case into the [high 40s] at Phoenix, the amount of lift and power in aircraft engines declines, and the result is that for any given runway length, you can carry less and less payload," Robert Mann, an industry analyst and former airline executive, said.

"As temperatures get that extreme, you have to offload so much fuel or passengers or cargo that it no longer makes sense to fly," he said.

ABC News Breakfast weatherman Nate Byrne explained:

"When the temperatures get that hot, the air is literally just not dense enough to make sure that all of the physics that works to help an aircraft get into the air are enough for it to do that safely."

Mr Mann said aircraft may also be hampered because the charts used in flight manuals to calculate aircraft performance are not written with such heat in mind, making it impossible for pilots to accurately calculate payloads and take-off speeds.

The flights affected by the heat tend to be on smaller regional carriers, which use planes that operate under lower maximum temperatures.

"It doesn't happen very often because these are exceedingly rare temperatures, but there's a point at which either runway length is insufficient or the speed is so high that the tires wouldn't be rated for it," Mr Mann said of those aircraft.

The heat can also create issues for ground crews, where pavement temperatures can reach more 66C, life-threatening conditions if workers are exposed to it for too long.